ISO 15788-1:1999 動物性および植物性の油脂—植物油中のスティグマスタジエンの測定—パート1：キャピラリーカラムガスクロマトグラフィーを使用したメソッド（参照メソッド） | ページ 2

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.

Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.

International Standard ISO 15788-1 was prepared by Technical Committee ISO/TC 34, Agricultural food products, Subcommittee SC 11, Animal and vegetable fats and oils.

ISO 15788 consists of the following parts, under the general title Animal and vegetable fats and oils — Determination of stigmastadienes in vegetable oils:

• Part 1: Method using capillary-column gas chromatography
• Part 2: Method using high-performance liquid chromatography

Annex A of this part of ISO 15788 is for information only.

Introduction

Significant amounts of hydrocarbons are formed in vegetable oils as a consequence of thermal treatments during the refining processes [1]. Among these hydrocarbons, 3,5-stigmastadiene, a steroidal compound, is the most abundant in all refined vegetable oils since it is derived from β-sitosterol by dehydration [2]. The 3,5-stigmastadiene is produced together with minor amounts of the 2,4-isomer and both substances give a single well-defined gas-chromatographic peak when the hydrocarbon fraction is analysed on a low polar column [3]. Therefore, the sum of both isomers can be easily quantified by gas-chomatographic analysis of the steroidal hydrocarbon fraction [2], [4].

For instance, for virgin olive oils, the usual oil production processes (pressure or centrifuging) do not produce measurable amounts of stigmastadienes (less than 0,01 mg/kg). In crude olive residue oil, small concentrations of stigmastadienes are found (ranging between 0,2 mg/kg and 3 mg/kg) due to the high temperatures applied during the drying of the raw olive residue.

In the refining processes, stigmastadienes are formed in all the steps involving high temperatures, such as bleaching and deodorizing, but more amounts are formed in the first step using acid bleaching earth than in the second [2]. Depending on the conditions applied during the refining process, commercial refined vegetable oils show stigmastadiene concentrations ranging between 1 mg/kg and 120 mg/kg and, therefore, the assessment of stigmastadienes allows not only the identification of thermally treated oils but also the detection of minor amounts of refined vegetable oils in virgin oils.

A method for the determination of stigmastadienes and the results of a collaborative study carried out under the auspices of the International Olive Oil Council were presented to the International Union of Pure and Applied Chemistry (IUPAC) Commission on Oils, Fats and Derivatives. The stigmastadiene content has been adopted as an identity criterion for virgin olive oils and the resulting analytical method has been adopted as an international standard method.

1 Scope

This part of ISO 15788 specifies a method for the determination of stigmastadienes in virgin vegetable oils containing low concentrations of these hydrocarbons, particularly in virgin olive oil.

This method is applicable to all vegetable oils although measurements are reliable only where the content of these hydrocarbons lies between 0,01 mg/kg and 4,0 mg/kg. The method is suited to detecting the presence of refined vegetable oils (olive, olive pomace, sunflower, palm, etc.) in virgin olive oils, since refined oils contain stigmastadienes and cold-extracted oils do not.

Bibliography